from __future__ import print_function
from string import ascii_lowercase

SYMBOLTABLE = list(ascii_lowercase)

def move2front_encode(strng, symboltable):
    sequence, pad = [], symboltable[::]
    for char in strng:
        indx = pad.index(char)
        sequence.append(indx)
        pad = [pad.pop(indx)] + pad
    return sequence

def move2front_decode(sequence, symboltable):
    chars, pad = [], symboltable[::]
    for indx in sequence:
        char = pad[indx]
        chars.append(char)
        pad = [pad.pop(indx)] + pad
    return ''.join(chars)

if __name__ == '__main__':
    for s in ['broood', 'bananaaa', 'hiphophiphop']:
        encode = move2front_encode(s, SYMBOLTABLE)
        print('%14r encodes to %r' % (s, encode), end=', ')
        decode = move2front_decode(encode, SYMBOLTABLE)
        print('which decodes back to %r' % decode)
        assert s == decode, 'Whoops!'